bors 88d69b72b4 Auto merge of #119099 - fmease:always-const-trait-bounds, r=fee1-dead ... Introduce `const Trait` (always-const trait bounds) Feature `const_trait_impl` currently lacks a way to express “always const” trait bounds. This makes it impossible to define generic items like fns or structs which contain types that depend on const method calls (\*). While the final design and esp. the syntax of effects / keyword generics isn't set in stone, some version of “always const” trait bounds will very likely form a part of it. Further, their implementation is trivial thanks to the `effects` backbone. Not sure if this needs t-lang sign-off though. (\*): ```rs #![feature(const_trait_impl, effects, generic_const_exprs)] fn compute<T: const Trait>() -> Type<{ T::generate() }> { /*…*/ } struct Store<T: const Trait> where Type<{ T::generate() }>:, { field: Type<{ T::generate() }>, } ``` Lastly, “always const” trait bounds are a perfect fit for `generic_const_items`. ```rs #![feature(const_trait_impl, effects, generic_const_items)] const DEFAULT<T: const Default>: T = T::default(); ``` Previously, we (oli, fee1-dead and I) wanted to reinterpret `~const Trait` as `const Trait` in generic const items which would've been quite surprising and not very generalizable. Supersedes #117530. --- cc `@oli-obk` As discussed r? fee1-dead (or compiler)		2023-12-27 19:24:31 +00:00
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src	Auto merge of #119099 - fmease:always-const-trait-bounds, r=fee1-dead	2023-12-27 19:24:31 +00:00
Cargo.toml	Clean up rustc_*/Cargo.toml.	2023-10-30 08:46:02 +11:00
messages.ftl	fallback default to None during ast-loweing for lifetime binder	2023-12-26 16:10:29 +08:00